N-glycosylation of CD97 within the EGF domains is crucial for epitope accessibility in normal and malignant cells as well as CD55 ligand binding

Institute of Anatomy, University of Leipzig, Leipzig, Germany.
International Journal of Cancer (Impact Factor: 5.09). 01/2005; 112(5):815-22. DOI: 10.1002/ijc.20483
Source: PubMed


CD97 is an EGF-TM7 receptor found on various carcinomas where expression levels correlate with dedifferentiation and tumor stage, smooth muscle cells and leukocytes. CD97 acts as an adhesion molecule by binding to its cellular ligand, CD55. In this study, we demonstrate that 2 immunodominant CD97 epitopes are not equally present in the various cell types. Differences were apparent in gastrointestinal tumors and smooth muscle cells where monoclonal antibodies (mAbs) to the first epidermal growth factor (EGF) domain (CD97(EGF)) showed a more restricted staining pattern than mAbs to the stalk region (CD97(stalk)). This discrepancy was not detectable in cultured gastrointestinal tumor cell lines. In fact, the selection of the CD97 mAb influences the result of clinical studies. Thus, we clarified the reason(s) for these differences in CD97 mAb staining on various cell types. We provide evidence that epitope accessibility for CD97(EGF) mAbs depends on N-glycosylation. Immunoprecipitation of CD97 from the Colo 205 tumor cell line revealed the established 78 and 83 kDa products, while a 52 and 57 kDa band were obtained from smooth muscle cells. N-glycosidase F reduced the size of CD97 in Colo 205 cells to 52-57 kDa. Culturing these cells with tunicamycin resulted in the same decrease in size and impaired CD97(EGF) mAb binding. As shown by site-directed mutagenesis, deletion of the N-glycosylation sites located within the EGF domains efficiently disturbed CD97(EGF) mAb immunoreactivity and, importantly, binding of CD55. In conclusion, CD97(EGF) epitope accessibility for mAbs and ligand binding is influenced by cell type-specific N-glycosylation.

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    • "It consists of a variable number of N-terminally located EGF domains, a long extracellular stalk, the 7-transmembrane domain, and a short intracellular C-terminal region [14–16]. It has been demonstrated that CD97 participates in the migration and invasion of tumor cells, which can be strengthened by CD55, the ligand for CD97 [17]. In gastric tumor tissues, the expression of CD55 was well correlated with that of CD97. "
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    ABSTRACT: CD97 as a member of the EGF-TM7 family with adhesive properties plays an important role in tumor aggressiveness by binding its cellular ligand CD55, which is a complement regulatory protein expressed by cells to protect them from bystander complement attack. Previous studies have shown that CD97 and CD55 both play important roles in tumor dedifferentiation, migration, invasiveness, and metastasis. The aim of this study was to investigate CD97 and CD55 expression in primary gallbladder carcinoma (GBC) and their prognostic significance. Immunohistochemistry was used to investigate the expression of CD97 and CD55 proteins in 138 patients with GBC. CD97 and CD55 were absent or only weakly expressed in the normal epithelium of the gallbladder but in 69.6% (96/138) and 65.2% (90/138) of GBC, respectively, remarkably at the invasive front of the tumors. In addition, CD97 and CD55 expressions were both significantly associated with high histologic grade (both P = 0.009), advanced pathologic T stage (P = 0.01 and 0.009, resp.) and clinical stage (both P = 0.009), and positive venous/lymphatic invasion (both P = 0.009). Multivariate analyses showed that CD97 (hazard ratio, 3.236; P = 0.02) and CD55 (hazard ratio, 3.209; P = 0.02) expressions and clinical stage (hazard ratio, 3.918; P = 0.01) were independent risk factor for overall survival. Our results provide convincing evidence for the first time that the expressions of CD97 and CD55 are both upregulated in human GBC. The expression levels of CD97 and CD55 in GBC were associated with the severity of the tumor. Furthermore, CD97 and CD55 expressions were independent poor prognostic factors for overall survival in patients with GBC.
    BioMed Research International 04/2012; 2012:587672. DOI:10.1155/2012/587672 · 2.71 Impact Factor
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    • "nomas frequently expressed CD97 stalk within tumor cells, the selectivity of CD97 mAbs significantly influences the prognostic value of CD97 in clinical studies (Wobus et al., 2004). We systematically investigated for the first time the expression and role of CD97 stalk and its cellular ligand CD55 in gastric car- cinomas. "
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    ABSTRACT: To explore the mechanism of development and aggressiveness in gastric carcinomas by investigating the expression and role of CD97 and its cellular ligand CD55 in gastric carcinomas. Tumor and corresponding normal mucosal tissue, collected from 39 gastric carcinoma patients, were examined by immunohistochemistry and RT-PCR for the expression of CD97 and CD55. CD97(stalk) was strongly stained on scattered tumor cells or small tumor cell clusters at the invasion front of gastric carcinomas. The expression of CD97(stalk) was frequently observed in tumors of stage I and T1 gastric carcinoma patients. The expression of CD97(stalk) between Stage I and Stage II, III, IV specimens showed significant difference (P<0.05), between T1 and T2, T3, T4 specimens also showed significant difference (P<0.05). Specimens with tumor invasion depth limited in mucosa of T1 specimens showed higher positive CD55 expression than specimens with the same tumor invasion depth in T2, T3, T4 specimens, the expression of CD55 between T1 and T2, T3, T4 specimens was significantly different (P<0.05). There was strong correlation between the distribution patterns of CD97(stalk) and CD55 on tumor tissues (r=0.73, P<0.05). Signet ring cell carcinomas frequently contained strong CD97(stalk) and CD55-staining. Our results suggest that CD97(stalk) is probably involved in the growth, invasion and aggressiveness of gastric carcinomas by binding its cellular ligand CD55. CD97(stalk) and CD55 could be useful as molecular markers for prognosis and therapy of gastric carcinoma patients.
    Journal of Zhejiang University SCIENCE B 09/2005; 6(9):913-8. DOI:10.1631/jzus.2005.B0913 · 1.28 Impact Factor
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